Index table generation in PVR applications for AVC video streams

ABSTRACT

One or more methods and systems of indexing an AVC video stream are presented. In one embodiment, the method comprises identifying one or more fields within a picture of an AVC video stream. In one embodiment, a field of the one or more fields indicates the beginning of each picture. In a second embodiment, a field of the one or more fields indicates a picture type of a picture. In a third embodiment, a field of the one or more fields indicates whether a picture is a reference or a non-reference picture. By determining that a picture is a non-reference picture, the picture may be discarded, thereby reducing the memory required to implement the indexing system while increasing the available memory size. In one embodiment, a system of indexing an AVC video stream comprises a control processor, a memory, and a set of instructions resident in the memory.

BACKGROUND OF THE INVENTION

Personal Video Recorder (PVR) applications require the generation ofindex tables in order to indicate the location and type of each picturein a video stream. PVRs utilize index tables on digital video as a meansto conveniently manipulate the video data by way of its hardware andsoftware. The index tables are often stored in a storage device such asa hard drive. By utilizing these index tables, PVRs allow a user toemploy one or more indexing techniques or trick modes that include timeshifting, pausing and fast forwarding video to provide a more desirableviewing experience for the user. The generation of such index tables area key component of any PVR application.

Unfortunately, the generation of such index tables may be an arduoustask for AVC (Advanced Video Coding) formatted digital video streamsbecause the AVC standard does not require the type of each picture to becoded at the picture level.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

Aspects of the invention provide for one or more methods and systems toindex the start or beginning of one or more pictures of an AVC videostream. Further aspects of the invention provide for a method and systemof determining the type of picture in an AVC video stream. Other variousaspects of the invention provide for increasing the available memorysize of a system by assessing the use of a picture so that it may bediscarded from memory after its presentation.

In one embodiment, a method of indexing one or more pictures transmittedin an AVC data stream comprises identifying a field of a slice of theone or more pictures of the AVC data stream, and determining a valueprovided by an identified field.

In one embodiment, a method of determining a picture type of a pictureusing one or more fields comprises locating the one or more fieldswithin each of one or more slice headers of one or more slices, parsingthe one or more fields, identifying one or more picture types associatedwith the one or more fields, determining if a first condition issatisfied, wherein the first condition assesses if each of the one ormore picture types comprises a first picture type, generating a firstpicture type decision if the first condition is satisfied, determiningif a second condition is satisfied, wherein the second conditionassesses if at least one of the one or more fields comprises a secondpicture type, generating a second picture type decision if the secondcondition is satisfied, determining if a third condition is satisfied,wherein the third condition assesses if the one or more fields comprisesa third picture type and not the second picture type, and generating athird picture type decision if the third condition is satisfied.

In one embodiment, a method of indexing an AVC video data streamcomprises locating a first field that provides a value of the firstmacroblock of a slice, determining the value, locating a second fieldthat provides a picture type indicator of the slice, and determining oneor more picture types associated with the slice.

In one embodiment, a method of reducing the amount of memory requiredfor indexing using an AVC video data stream comprises locating a fieldwithin a picture of one or more pictures of the AVC video data stream,reading the field, determining whether the picture is a referencepicture or a non-reference picture based on the reading, storing thepicture into a memory after its presentation, if the picture is areference picture, and discarding the picture after its presentation, ifthe picture is a non-reference picture.

In one embodiment, a system of indexing an AVC video data streamcomprises a control processor, a circuitry, a memory, and a set ofinstructions resident in the memory.

These and other advantages, aspects, and novel features of the presentinvention, as well as details of illustrated embodiments, thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an operational flow diagram illustrating an algorithm used toindex AVC video in accordance with an embodiment of the invention.

FIG. 2 is a block diagram of an AVC indexing system in accordance withan embodiment of the invention.

FIG. 3 is a relational block diagram of a personal video recorder (PVR)system incorporating the AVC indexing system referenced in FIG. 2, inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the present invention may be found in a system and method ofindexing AVC (Advanced Video Coding) video data streams. The one or moresystems and/or methods presented herein conform or comply with DraftITU-T Recommendation and Final Draft International Standard of JointVideo Specification (ITU-T Rec. H.264|ISO/IEC 14496-10 AVC), which isincorporated herein by reference in its entirety. The aforementionedspecification may be obtained from ISO (International Organization forStandardization), Geneva, Switzerland.

In one embodiment, the method comprises identifying one or more fieldswithin a picture of an AVC video stream. In one embodiment, a field ofthe one or more fields indicates the beginning of each picture. In asecond embodiment, a field of the one or more fields indicates a picturetype of a picture. In a third embodiment, a field of the one or morefields indicates whether a picture is a reference or a non-referencepicture. By determining that a picture is a non-reference picture, thepicture may be discarded after its presentation, thereby reducing thememory required to implement the indexing system while increasing theavailable memory size. In one embodiment, a system of indexing an AVCvideo stream comprises a control processor, a memory, and a set ofinstructions resident in the memory. The system may be termed an AVCindexing system. The AVC indexing system may be incorporated as asubsystem into a personal video recorder (PVR) in order to facilitateindexing of the AVC video stream.

FIG. 1 is an operational flow diagram illustrating an algorithm used toindex AVC video in accordance with an embodiment of the invention. Atstep 104, the algorithm parses a field within a picture that indicateswhether the picture comprises a reference picture or a non-referencepicture. The picture in which the field is parsed may comprise a firstpicture among one or more pictures of an AVC video stream. In oneembodiment, the field is located within a NAL (network abstractionlayer) unit header. In one embodiment, a reference or non-referencepicture is indicated by the value of this field. In one embodiment, ifthe value of the field is zero, the value indicates that the picture isdiscardable (i.e., may be discarded after its presentation). On theother hand, a non-zero value, such as the value 1, indicates that thepicture is not discardable. The field may comprise a field within aslice header of one or more slices of the picture. In one embodiment,the field may comprise a nal_ref_idc field in compliance with DraftITU-T Recommendation and Final Draft International Standard of JointVideo Specification (ITU-T Rec. H.264|ISO/IEC 14496-10 AVC). Discardingsuch non-referenced pictures may reduce the memory required in theimplementation of the AVC indexing system. Furthermore, discardingnon-referenced pictures may increase the available memory size, therebyimproving performance of the AVC indexing system and its memorydependent peripheral circuitry. During step 104, a non-reference picturemay be marked as discardable using the exemplary nal_ref_idc field; as aresult, it may be discarded from memory after being used. Suchnon-reference pictures are not used when decoding additional incomingpictures. At step 108, the location of a picture is indexed when a fieldwithin a slice of one or more slices in a picture indicates thebeginning of the picture. In one embodiment, the field that indexes thestart of a picture may comprise a first_mb_in_slice field in compliancewith Draft ITU-T Recommendation and Final Draft International Standardof Joint Video Specification (ITU-T Rec. H.264|ISO/IEC 14496-10 AVC).For example, the location of the beginning of a picture is indexed whenthe contents of the first_mb_in_slice field equals the value zero. Inreference to the aforementioned steps 104 and 108, the order of thesteps may be interchanged such that indexing the location of a picturemay occur prior to marking a picture discardable. At step 110, avariable, termed PT (i.e., implying picture type) is initialized with avalue corresponding to an I picture. The variable, PT, is used to storeone or more values that indicate picture type. The picture type isindicated by examining one or more fields in a slice header of one ormore slices in a picture. The field of the slice header is parsed andexamined by the AVC indexing system. In the flow diagram of FIG. 1, thevariable PT may correspond to a register or location within a memory ofthe AVC indexing system that stores a value that corresponds to aparticular picture type. In one embodiment, the picture type maycomprise a B, I, or P type of picture, as defined in Draft ITU-TRecommendation and Final Draft International Standard of Joint VideoSpecification (ITU-T Rec. H.264|ISO/IEC 14496-10 AVC). Prior to parsingand examining the first slice of the picture by the AVC indexing system,the variable PT, by default, stores a value that corresponds to an Ipicture. At step 112, the AVC indexing system performs a decode of afield of a slice in a picture; in one embodiment the field comprises aslice_type field. The slice may comprise a first slice of a picture ofan AVC video stream. At step 116, the first slice of the picture isexamined in terms of the picture type. For example, the contents of theslice_type field within the slice is examined to see if the associatedpicture is a P picture. If the slice_type field indicates that thepicture type is a P type of picture, then the variable PT is set to avalue that corresponds to that of a P picture, as illustrated in step120. Otherwise, the process proceeds to step 124, in which, anassessment is made whether the slice indicates that the picture is a Bpicture. If the slice_type field indicates that the picture is indeed aB picture, the process proceeds to step 128, in which the variable PT isset to a value that corresponds to a B picture. Otherwise, at step 132,the next slice header of the next slice in the picture is parsed. Next,at step 136, the AVC indexing system determines if the next slice is thefirst slice in the next picture. In one embodiment, as previouslymentioned, the start (or first slice) of a picture is indexed when thefirst_mb_in_slice field has value equal to zero. For example, the AVCindexing system decodes the data in the first_mb_in_slice field todetermine if the slice corresponds to the first slice in the picture. Ifthe first_mb_in_slice is not equal to zero, the next slice is not thefirst slice of the next picture, and the process jumps back to step 112,in which the slice type field of the next slice is decoded. If, on theother hand, the first_mb_in_slice field is equal to zero, the processproceeds at step 140. At step 140, the value of PT is read or decoded inorder to determine the picture type. At step 144, the AVC indexingsystem determines whether additional picture(s) need to be processed bythe AVC indexing system. If there are additional pictures, the processproceeds at steps 104/108, in which the discardability of a picture isascertained and indexing of the starting location of the next picture isperformed. Otherwise, if the current picture comprises the last picturein the AVC video stream, the process ends.

The following table provides an example of the values of the parameters(or variables) used in the algorithm previously described in FIG. 1.These parameters comprise the first_mb_in_slice, slice_type, andnal_ref_idc fields. TABLE #1 Picture 0 Picture 1 Picture 2 Picture 3(I-Picture) (B-Picture) (P-Picture) (B-Picture) first_mb_in_slice 0 4 210 15 28 0 10 20 0 5 15 24 slice_type I I I B P B I P P P B I Pnal_ref_idc 1 1 1 0  0  0 1 1  1 0 0  0  0 Slice Parsed By 1 2  3 4 5  6 7 8 9 Algorithm Discardable picture No Yes No Yes

Table #1 comprises five rows. The first row comprises entries thatprovide the macroblock number of the first macroblock in each slice of apicture. As indicated in Table #1, the first macroblock of each slice isindexed. For example, picture #0 has three slices, in which, the firstmacroblock of the three slices are located at macroblock #0, #4, and#21. The second row comprises entries that provide the slice type of aparticular slice as determined by the slice_type field in the sliceheader of a picture. As illustrated in Table #1, picture #0 comprises anI picture because, the slice_type field of each slice indicates that thepicture type is an I picture. In picture #1, for example, the picture isdetermined to be a B picture immediately because the first sliceindicates that the picture type is a B picture. The third row comprisesentries that provide an indication whether the slice is associated witha reference picture or a non-reference picture. As discussed previously,if the picture is determined to be a non-reference picture, it may bediscarded after presentation. Otherwise, the picture is a referencepicture that may be utilized in the decoding of subsequent pictures. Asillustrated in Table #1, the values for the nal_ref_idc field areconsistent throughout all slices within a picture. As mentioned earlier,when nal_ref_idc=0, the picture is discardable. The fourth row comprisesentries that indicate the slice number parsed by the algorithm. Asillustrated in Table #1, the second and third slices of picture #1 arenot parsed and analyzed because the first slice has determined thatpicture #1 is a B picture. Hence the picture is categorized as a Bpicture, and the process proceeds with the reading of the next picture(picture #2). As soon as the algorithm determines the picture is a Bpicture, additional slices in the picture need not be analyzed, and thealgorithm jumps to the next picture. This may be further observed usingthe second slice of picture #3; the picture is determined to be a Bpicture at the second slice. As a consequence, the third and fourthslices of picture #3 do not need to be further parsed and analyzed. Inreference to picture #2, all slices are parsed and analyzed since thereare no slices that indicate the picture is a B type of picture. Picture#2 is categorized as a P picture since there is at least one slice thatindicates that picture #2 is a P picture while there are no slices thatindicate that picture #2 is a B picture. The fifth row of Table #1indicates whether the associated picture is discardable, and is directlyrelated to the third row of Table #1. For example, if nal_ref_idc=0 asshown in picture #1, the picture is discardable, and is indicated by a“yes”. In another example, if nal_ref_idc=1, as shown in picture #2, thepicture is not discardable, and is indicated by a “no”.

FIG. 2 is a block diagram of an AVC indexing system 204, in accordancewith an embodiment of the invention. The AVC indexing system 204comprises a memory 208, a control processor 216, and circuitry 220. Asshown, a set of software instructions or firmware 212, resident in thememory 208, is executed by way of processing performed by the controlprocessor 216. AVC video data may be received and processed by thecircuitry 220 by way of execution of the firmware 212 resident in thememory 208. The memory 208 may comprise a read only memory (ROM) such asa non-volatile ROM. The circuitry 220 may comprise one or moreinterfaces and logic devices used in the processing of data in relationto the operational flow diagram of FIG. 1. The firmware 212 mayfacilitate data processing of the AVC video stream in relation to thesteps performed in FIG. 1. Use of the AVC indexing system 204facilitates the indexing of picture position, picture type, anddiscardability information of one or more pictures in an AVC videostream. In addition, the circuitry 220 may comprise one or more logicdevices that facilitate the generation of a PVR index table thatincorporates the picture position information, picture type, anddiscardability information. The PVR index table is stored in a storagedevice such as a hard disk drive.

FIG. 3 is a relational block diagram of a personal video recorder (PVR)system incorporating the AVC indexing system referenced in FIG. 2, inaccordance with an embodiment of the invention. The PVR system comprisesa digital demodulator 304, a data processor 308, a first data buffer312, a storage device 316, a PVR indexing system 320 comprising the AVCindexing system 322, a second data buffer 324, and a descrambler/decoder328. As illustrated in FIG. 3, a digital video stream is input in thedigital demodulator 304. In one embodiment, the digital video streamcomprises an AVC (i.e, H.264 or JVT) type of digital video stream. TheAVC video stream may be received from a telecommunications operator orcarrier. One or more selectable video programs or channels may bedelivered from the AVC video stream. In this embodiment, the digitaldemodulator 304 functions to demodulate a received digital video streamto an appropriate baseband signal. Thereafter, the baseband video signalis received by a processor such as the data processor 308. The dataprocessor 308 selects a particular program or channel by filtering outAVC video data, for example, and subsequently decrypting the filtereddata. Next, the data processor 308 may reconfigure the filtered data andsubsequently store the reconfigured data in the first data buffer 312.The first data buffer 312 facilitates recording or writing of thefiltered AVC data into the storage device 316. The storage device 316may comprise an exemplary hard disk drive or other comparable device.

While recording to a storage device 316, the AVC indexing system 322 mayoptionally employ the algorithm described and referenced in FIG. 1, inorder to effectively and efficiently index, type, and determine thediscardability of the one or more pictures received from the AVC videostream. The values of the parameters of the algorithm (described inreference to FIG. 1) may be stored within the storage device 316. Forexample, the start (or beginning) of the one or more pictures may bedetermined, and its position information may be stored in the storagedevice 316 by way of control provided by the AVC indexing system 322. Inaddition, a picture's picture type (I, P, or B) and its discardabilitymay be stored in the storage device 316. Information such as positioninformation, picture type, and discardability attributes may be used togenerate a PVR index table. The index table, of course, is used tofacilitate various trick modes and indexing techniques. The AVC indexingsystem 322 facilitates the generation of the index table, improving AVCvideo playback functionality and operational performance of the PVRsystem. The PVR indexing system 320 may comprise one or more types ofindexing systems, in addition to the AVC indexing system 322. The secondbuffer 324 facilitates delivery of AVC video data into thedescrambler/decoder 328. Any timing changes resulting from controlprovided by the PVR indexing system 320 or AVC indexing system 322 areobviated using the second buffer 324. The selected program or channel issubsequently descrambled/decoded by the descrambler/decoder 328.Thereafter, the program or channel is displayed by a monitor ortelevision or any appliance capable of visually providing the selectedvideo to a viewer. It is contemplated that one or more of the elements304, 308, 312, 316, 320, 322, 324, 328 described in FIG. 3 may beincorporated into a set-top-box in order to interface and process anyAVC data stream provided by the telecommunications operator.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiment disclosed, but that the invention will include allembodiments falling within the scope of the appended claims.

1. A method of indexing one or more pictures transmitted in an AVC datastream comprising: identifying a field of a slice of said one or morepictures of said AVC data stream; and determining a value provided by anidentified field.
 2. The method of claim 1 wherein said indexingindicates the beginning of each picture in said one or more pictures. 3.The method of claim 1 wherein said field comprises a field that providesthe value of the first macroblock in said slice of said one or morepictures of said data stream.
 4. The method of claim 3 wherein saidfield comprises a first_mb_in_slice field as defined in ITU-T Rec.H.264|ISO/IEC 14496-10 AVC.
 5. A method of determining a picture type ofa picture using one or more fields, each of said fields associated witha slice of one or more slices, said one or more slices associated with apicture, said method comprising: locating said one or more fields withineach of one or more slice headers of said one or more slices; parsingsaid one or more fields; identifying one or more picture typesassociated with said one or more fields; determining if a firstcondition is satisfied, said first condition assessing if each of saidone or more picture types comprises a first picture type; generating afirst picture type decision if said first condition is satisfied;determining if a second condition is satisfied, said second conditionassessing if at least one of said one or more fields comprises a secondpicture type; generating a second picture type decision if said secondcondition is satisfied; determining if a third condition is satisfied,said third condition assessing if said one or more fields comprises athird picture type and not said second picture type; and generating athird picture type decision if said third condition is satisfied.
 6. Themethod of claim 5 wherein said first picture type comprises an I picturefield as defined in ITU-T Rec. H.264|ISO/IEC 14496-10 AVC.
 7. The methodof claim 5 wherein said second picture type comprises a B picture fieldas defined in ITU-T Rec. H.264|ISO/IEC 14496-10 AVC.
 8. The method ofclaim 5 wherein said third picture type comprises a P picture field asdefined in ITU-T Rec. H.264|ISO/IEC 14496-10 AVC.
 9. The method of claim1 wherein said value comprises a fixed value.
 10. The method of claim 9wherein said fixed value comprises the value zero.
 11. A method ofindexing an AVC video data stream comprising: locating a first fieldthat provides a value of the first macroblock of a slice; determiningsaid value; locating a second field that provides a picture typeindicator of said slice; and determining one or more picture typesassociated with said slice.
 12. The method of claim 11 wherein saidfirst field comprises a first_mb_in_slice field as defined in ITU-T Rec.H.264|ISO/IEC 14496-10 AVC.
 13. The method of claim 11 wherein saidsecond field comprises a slice_type field as defined in ITU-T Rec.H.264|ISO/IEC 14496-10 AVC.
 14. The method of claim 11 furthercomprising: locating a third field that provides a reference pictureindicator of said slice; and determining whether said picture is adiscardable picture based on said reference picture indicator.
 15. Themethod of claim 14 wherein said third field comprises a nal_ref_idcfield as defined in ITU-T Rec. H.264|ISO/IEC 14496-10 AVC.
 16. A methodof reducing the amount of memory required for indexing using an AVCvideo data stream, said method comprising: locating a field within apicture of one or more pictures of said AVC video data stream; readingsaid field; determining whether said picture is a reference picture or anon-reference picture based on said reading; storing said picture into amemory, after its presentation, if said picture is a reference picture;and discarding said picture if said picture is a non-reference picture.17. A video system comprising: a control processor; a circuitry; amemory; and a set of instructions resident in said memory, said set ofinstructions causing indexing of an AVC video data stream.
 18. Thesystem of claim 17 wherein said set of instructions is used to locateand identify one or more fields within each of one or more slice headersof said one or more slices.
 19. The system of claim 18 wherein said setof instructions is used to parse said one or more fields, identify oneor more picture types associated with said one or more fields, determineif each of said one or more picture types comprises a first picturetype, determine if at least one of said one or more fields comprises asecond picture type, and determine if said one or more fields comprisesa third picture type and not said second picture type.
 20. The system ofclaim 19 wherein a first picture type decision is made if each of saidone or more picture types comprises said first picture type.
 21. Thesystem of claim 19 wherein a second picture type decision is made if atleast one of said one or more fields comprises said second picture type.22. The system of claim 19 wherein a third picture type decision is madeif at least one of said one or more fields comprises said third picturetype and not said second picture type.